diff --git a/src/transforms/normalize.d.ts b/src/transforms/normalize.d.ts
index 316f2240cd..a5219e22f5 100644
--- a/src/transforms/normalize.d.ts
+++ b/src/transforms/normalize.d.ts
@@ -14,20 +14,87 @@ export type NormalizeBasisName =
   | "extent"
   | ReducerPercentile;
 
-export type NormalizeBasisFunction = (index: number[], values: any[]) => any;
+export type NormalizeBasisFunction = (index: number[], values: any[]) => number;
 
+/** How to normalize series values. */
 export type NormalizeBasis = NormalizeBasisName | NormalizeBasisFunction;
 
+/** Options for the normalize transform. */
 export interface NormalizeOptions {
   basis?: NormalizeBasis;
 }
 
+/**
+ * Groups data into series using the first channel of *z*, *fill*, or *stroke*
+ * (if any), then derives new *x*, *x1*, and *x2* channels for each
+ * corresponding input channel by normalizing to the given *basis*. For example,
+ * if the series values are [*x₀*, *x₁*, *x₂*, …] and the *first* basis is used,
+ * the derived series values would be [*x₀* / *x₀*, *x₁* / *x₀*, *x₂* / *x₀*, …]
+ * as in an index chart.
+ *
+ * The **basis** option specifies how to normalize series values. It can be:
+ *
+ * * *first* (default) - the first value, as in an index chart
+ * * *last* - the last value
+ * * *min* - the minimum value
+ * * *max* - the maximum value
+ * * *mean* - the mean value (average)
+ * * *median* - the median value
+ * * *pXX* - the percentile value, where XX is a number in [00,99]
+ * * *sum* - the sum of values
+ * * *extent* - the minimum is mapped to zero, and the maximum to one
+ * * *deviation* - subtract the mean, then divide by the standard deviation
+ * * a function to be passed an array of series values, returning a number
+ */
 export function normalizeX<T>(options?: T & NormalizeOptions): Transformed<T>;
-
 export function normalizeX<T>(basis?: NormalizeBasis, options?: T): Transformed<T>;
 
+/**
+ * Groups data into series using the first channel of *z*, *fill*, or *stroke*
+ * (if any), then derives new *y*, *y1*, and *y2* channels for each
+ * corresponding input channel by normalizing to the given *basis*. For example,
+ * if the series values are [*y₀*, *y₁*, *y₂*, …] and the *first* basis is used,
+ * the derived series values would be [*y₀* / *y₀*, *y₁* / *y₀*, *y₂* / *y₀*, …]
+ * as in an index chart.
+ *
+ * The **basis** option specifies how to normalize series values. It can be:
+ *
+ * * *first* (default) - the first value, as in an index chart
+ * * *last* - the last value
+ * * *min* - the minimum value
+ * * *max* - the maximum value
+ * * *mean* - the mean value (average)
+ * * *median* - the median value
+ * * *pXX* - the percentile value, where XX is a number in [00,99]
+ * * *sum* - the sum of values
+ * * *extent* - the minimum is mapped to zero, and the maximum to one
+ * * *deviation* - subtract the mean, then divide by the standard deviation
+ * * a function to be passed an array of series values, returning a number
+ */
 export function normalizeY<T>(options?: T & NormalizeOptions): Transformed<T>;
-
 export function normalizeY<T>(basis?: NormalizeBasis, options?: T): Transformed<T>;
 
+/**
+ * Given a normalize *basis*, returns a corresponding map implementation for use
+ * with the map transform, allowing the normalization of arbitrary channels
+ * instead of only *x* and *y*. For example, to normalize the *title* channel:
+ *
+ * ```js
+ * Plot.map({title: Plot.normalize("first")}, {x: "Date", title: "Close", stroke: "Symbol"})
+ * ```
+ *
+ * The **basis** option specifies how to normalize series values. It can be:
+ *
+ * * *first* (default) - the first value, as in an index chart
+ * * *last* - the last value
+ * * *min* - the minimum value
+ * * *max* - the maximum value
+ * * *mean* - the mean value (average)
+ * * *median* - the median value
+ * * *pXX* - the percentile value, where XX is a number in [00,99]
+ * * *sum* - the sum of values
+ * * *extent* - the minimum is mapped to zero, and the maximum to one
+ * * *deviation* - subtract the mean, then divide by the standard deviation
+ * * a function to be passed an array of series values, returning a number
+ */
 export function normalize(basis: NormalizeBasis): Map;